Q: Loud knocking noise and engine is shaking.

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After accelerating down the road yesterday, mistakenly turned O/D "off" and tried to pass a slow-moving car. Engine revved up without gaining speed, then kicked back, followed by a loud repetitive knocking sound (as well as the check engine light flashing). Vehicle now continues to knock loudly whenever idling, and becomes noticeably louder when opening the throttle (accelerating/decelerating). Oil was low (so topped it off), and is still making noise. The noise appears to be coming from the engine and nowhere else on the car.

My car has 150000 miles.
My car has an automatic transmission.

Hi there. When passing a vehicle and turning off the overdrive at the same time with the pedal on the floor will be like trying to shift a vehicle without the clutch in a manual transmission driven vehicle. The rpm’s spike to the max and make the engine have a red line. What probably happened is the engine spun a rod bearing or damaged the engine causing the knocking noise. Check the codes on the ECM (computer) to see what is stored. When the check engine light flashes that means that the issue is happening right at that moment. I recommend seeking out a professional, such as one from Your Mechanic, to help you diagnose an engine knock.

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